一次全省性强雷暴天气的地闪特征

2009年6月26日浙江出现全省范围的雷暴天气,此次过程中出现的地闪频数是自2006年闪电定位系统建立以来出现最多的一次。利用闪电定位实测资料、加密雨量站雨量实况以及多普勒天气雷达产品,对这一过程的地闪特征进行了分析。结果表明:此次地闪以负地闪为主,负地闪广泛分布于25～55dBz雷电回波区域内,而正闪多出现在25～35dBz回波中;地闪多出现在回波发展和前进的一侧,且密集分布在回波的梯度最大处,强回波中心处地闪较少出现;在回波开始减弱到中心强度为35dBz左右的区域没有地闪发生。地闪频数与全省过程累积降水量有很好的相关性,地闪的出现及其频数的增加意味着影响某地的强对流风暴正在发展或正向本地移来,对于单站来说雨强峰值滞后于地闪频数峰值半个小时以上,对于全省累积降水量则提前1～2h。因此地闪资料可以作为强对流天气的短时强降水预报的预警依据。

Characteristics of a Cloud to Ground Lightning Event during a Large Scale Strong Storm

A whole-province range thunderstorm occurred in Zhejiang Province on 26 June 2009,and the occurrence frequency of cloud-to-ground lightning in this thunderstorm is the highest since the establishment of the lightning position system in 2006.By means of the observation data from the lightning position system,the intensive rainfall observation system,and Doppler radar,the characteristics of the cloud-to-ground lightning process are analyzed.The results indicate that lightning strokes were mainly negative;in the lightning echo image,negative strokes were mostly distributed in the area of 25 dBz to 55 dBz,and positive strokes were usually in the area of 25 dBz to 35 dBz;lightning strokes occurred mostly on the side of echo development or advancement,distributed around the area with maximum gradients,and there seldom appeared lightning strokes around a strong echo center;the frequency of cloud-to-ground lightning was correlated closely with the accumulated precipitation of the whole province during the thunderstorm.The peak value of precipitation lagged more than 0.5 hour behind the peak value of the frequency of cloud-to-ground lightning,and the accumulated precipitation of the whole province occurred 1 to 2 hours behind the peak value of the frequency of cloud-to-ground lightning.Therefore,the cloud-to-ground lightning data can be used as a basis in short-range severe precipitation forecasting.